Hammering Apparatus

ABSTRACT

Hammering apparatus functioning with a pressurized medium, such as a pressure fluid of a hydraulic system which hammering apparatus comprises an elongated body ( 19 ) to be attached to a power tool, a movable impact mass ( 10 ) adjusted to rest on the body ( 19 ) for which impact mass a linear control part is adjusted to the mentioned body ( 19 ) and an arrangement for lifting up the movable mass ( 10 ) for the impact comprising the first cylinder ( 20 ) and a piston ( 16 ) which can be moved in it with the help of pressure fluid and a piston rod ( 1 ) in which case in the arrangement the mentioned piston rod ( 1 ) is attached to the mentioned mass ( 10 ) and comprises a valve arrangement ( 15 ) with the help of which the pressure of the hydraulic fluid can be directed to the first cylinder ( 20 ) to the other side of the piston ( 16 ) for the uplifting of the mass ( 10 ) and the mentioned pressure can be suddenly reduced when the mass ( 10 ) is being directed to impact. During the impact of the mass ( 10 ) the hydraulic fluid or a part of it coming back from the cylinder space ( 6 ) of the first cylinder ( 20 ) can be directed to an expanding space ( 2 ) inside the piston rod ( 1 ) with the help of a valve arrangement ( 15 ) in which case a harmful back pressure caused by the hydraulic fluid being removed from the front of the piston ( 16 ) is essentially reduced.

Invention relates to a hammering apparatus functioning with apressurized medium, such as with a pressure fluid of a hydraulic system(pressure medium) which hammering apparatus comprises an elongated bodywhich can be attached to a power tool, a movable impact mass adjusted tobe resting on the body for which impact mass a linear control part isadjusted to the mentioned body and an arrangement for lifting themovable mass up for the impact comprising the first cylinder and apiston which can be moved in it with the help of a pressure fluid andcomprising the piston rod in which case in the arrangement the mentionedpiston rod is attached to the mentioned mass and comprises a valvearrangement with the help of which the pressure of the hydraulic fluidcan be directed to the first cylinder to the other side of the pistonfor the uplifting of the mass and the mentioned pressure can be reducedsuddenly when the mass is being directed to impact.

A hammering apparatus performing impacts downwards with the help of amass which can be lifted up is previously known for example from thepublication WO 03097945 in which several hydraulic cylinders are locatedoutside the mass with which cylinders the mass is both lifted up andwith the help of them also pressure is allocated to the gas spaceslocated at the other side of the pistons located in the cylinders withwhich pressure the mass is accelerated during the impact. For theduration of the impact the hydraulic pressure is removed from thecylinders. This solution has the disadvantage that during the impact thehydraulic fluid cannot be removed from the cylinder fast enough becauseit must be directed along the return line to a non-pressurized tank ofthe system. The return line creates back pressure and the impact whichis performed with compressed gas stays inefficient to a certain extent.The flow resistances of the return line thus create a problem whensudden back flow of the hydraulic fluid is required.

The above mentioned solution has also the disadvantage that the devicebecomes broad when the cylinders are located at the sides of the movablemass. The forces directed to the mass must be directed from thecylinders in sideways with the help of special arms in which case thearms become very heavy. It is difficult to make guide bars which directthe motion for the mass because the cylinders are located at the sameplace outside the mass. Each cylinder requires its own valve because thevalves must be installed as close to the cylinder as possible. Furtherit is difficult to get efficient cooling to the gas spaces located inthe cylinders.

With the hammering apparatus according to the invention essentialimprovements can be achieved to the known prior art and it ischaracteristic of the invention that during the impact of the mass thehydraulic fluid coming from the cylinder space of the first cylinder ora part of it can be directed to an expanding space inside the piston rodwith the help of a valve arrangement in which case a harmful backpressure caused by the hydraulic fluid being removed from the front ofthe piston is essentially reduced.

The advantage of the invention is the fact that during the accelerationof the mass the back pressure caused by the hydraulic fluid beingremoved suddenly from the cylinder can be essentially reduced when itcan be directed for a while to a nearby space expanding exactly at thesame time. When the mass is being lifted up to be effective, thehydraulic fluid is removed from this space to the return line but itsremoval does not have to be sudden. Thus in the invention a breathingspace is created to the hammering apparatus which space receivespressure fluid at the same time as the impacts occur and removes it atthe right time.

With the help of the structure according to the invention also theforces moving the mass can be organized in the back of the mass in orderto affect at the same line on which the mass is moving, too. Further anefficient cooling can be achieved to the cylinder spaces in which thegas becomes warmer due to compression when a changing hydraulic fluidwhich has a lower temperature circulates behind a wall which conductswarmth well and cools gas spaces through the wall. With the hammeringapparatus one can utilize a lot piston strokes which deviate from eachother and the one can utilize movements of the mass when the mass can belifted even to its highest position without the gas being squeezedexcessively although also a pre-pressure would be set for the gas.

In the following the invention is described more detailed by referringto the accompanying drawings in which

FIG. 1 shows a device according to the invention as a side view.

FIG. 2 shows the device of the FIG. 1 to which impact mass and thestructures required by it have been added.

In the FIG. 1 a hammering apparatus is shown from which a hollow arm 1coming out functions both as a lifting arm when the impact mass is beinglifted up and when the mass impacts to it functions as an arm conveyingaccelerating force. At the end of the arm 1 there is an attaching part 9with which it is attached to the impact mass. The arm 1 functions alsoas a piston rod for the piston 16 which is moved with hydraulicpressure. The hydraulic pressure is directed from the valve 15 along apipe 14 to the front side (left side) of the piston 16. There is acylinder space 4 at the backside (right side) of the piston 16 whichcylinder space is restricted to be an annular space by an inner pipe 3.A cylinder liner 20 functions as its outer surface.

The piston 16 and the piston rod 1 slide sealed on top of the innerpipe. The cylinder space 4 is filled with gaseous nitrogen to anappropriate pre-pressure. Gaps 17 are directed from the cylinder space 4to an annular space 5 located outside of it which annular space thusalso functions as a store of the gaseous nitrogen and also becomespressurized as the space 4 becomes pressurized due to the gaps 17. Theoutermost pipe 21 forms the outer surface of the annular space 5. Whenthe gaseous nitrogen streams all the time through the gaps 17 to theannular space 5 and away from there when the hammering apparatus is atwork, the hydraulic fluid directed to the annular space 6 coolsefficiently the gaseous nitrogen which aims to become warmer due tocontinuous compression and a pressure decrease following it.

The piston 16 performs the uplifting of the mass 10 and the cylinderspace 6 located in front of it receives the pressurized hydraulic fluidalong the pipe 14. During the impact the hydraulic fluid returns alongthe same pipe 14 as a very sudden burst. So that no back pressure wouldget created, the return liquid is directed to the inner space 2 of theinner pipe 3 with the help of a valve arrangement 15 which inner spaceis a space expanding at the very moment because the piston rod 1 movesoutwards. Only a short pipe 14 with a relatively large diameter is leftfor the pressure fluid to run during the impact. Due to this thepressure fluid can be removed suddenly from the cylinder space 6. Whenthe mass 10 is lifted up, the pressure fluid has more time to go awayfrom the inner space 2 of the piston rod 1 and the inner pipe 3 to thereturn line.

The changing pressure fluid located inside the inner pipe 3 also coolsefficiently the compressible gas inside the cylinder space 4.

In the FIG. 2 a hammering apparatus of the FIG. 1 is shown located tothe right end of the shaft tube 19. The shaft tube 19 functions also asthe control element of the impact mass 10 when the impact mass slides inthe shaft tube 19 when the hammering apparatus lifts it up andaccelerates it for the impact downwards. The impact mass 10 has amovement space 12. The impact mass 10 hits the piece 13. The wholehammering apparatus is attached for example to the end of the boom of anexcavator from the part 11 attached to the shaft tube 17 when one workswith it. With the help of an opened stage of the valve 15 shown by theFIG. 1 the length of the uplifting of the mass is adjusted.

1. Hammering apparatus functioning with a pressurized medium, such as apressure fluid of a hydraulic system which hammering apparatus comprisesan elongated body (19) to be attached to a power tool, a movable impactmass (10) adjusted to rest on the body (19) for which impact mass alinear control part is adjusted to the mentioned body (19) and anarrangement for lifting up the movable mass (10) for the impactcomprising the first cylinder (20) and a piston (16) which can be movedin it with the help of pressure fluid and a piston rod (1) in which casein the arrangement the mentioned piston rod (1) is attached to thementioned mass (10) and comprises a valve arrangement (15) with the helpof which the pressure of the hydraulic fluid can be directed to thefirst cylinder (20) to the other side of the piston (16) for theuplifting of the mass (10) and the mentioned pressure can be suddenlyreduced when the mass (10) is being directed to impact, characterized inthat during the impact of the mass (10) the hydraulic fluid or a part ofit coming back from the cylinder space (6) of the first cylinder (20)can be directed to an expanding space (2) inside the piston rod (1) withthe help of a valve arrangement (15) in which case a harmful backpressure caused by the hydraulic fluid being removed from the front ofthe piston (16) is essentially reduced.
 2. Hammering apparatus accordingto the claim 1, characterized in that the piston rod (1) of the firstcylinder (20) is hollow in which case it is adjusted to move sealed ontop of the inner pipe (3) and the inner space (2) of the inner pipe (3)and the inner space (2) of the piston rod (1) function as an expandingspace being able to receive hydraulic fluid which is to be directed tothe return line at the same time as the impacts occur and during theuplifting of the mass (10) the movement of the piston rod (1) removeshydraulic fluid from the mentioned inner space (2) to thenon-pressurized return line of the hydraulic system.
 3. Hammeringapparatus according to the claim 1, characterized in that the valvearrangement (15) is adjusted to open a passage for the pressure fluidfrom the inner space (2) of the piston rod (1) and the inner pipe (3) tothe return line of the hydraulic system when the mass (1) is beinglifted up and is adjusted to open a passage for the hydraulic fluidcoming back along the pipe (14) to the mentioned inner space (2) whenthe mass (10) is accelerated for the impact.
 4. Hammering apparatusaccording to the claim 1, characterized in that the annular space (5),cylinder space (4) and the inner pipe (3) are located coaxially inrelation to each other.
 5. Hammering apparatus according to the claim 1,characterized in that a space (5) which has a volume which staysconstant and is connected through gaps (17) is attached to the part (4)of the cylinder space of the first cylinder (20) filled with gas. 6.Hammering apparatus according to the claim 5, characterized in that thespace (5) staying constant and is connected with the help of the gaps(17) is formed to be an annular space around the first cylinder (20).